Aliphatic polycarbonates (“APCs”) are biocompatible and biodegradable materials with numerous uses ranging from high-performance applications in material science to use as biodegradable consumer packaging. Many applications of APCs require a colorless, metal free polymer that decomposes cleanly without leaving a residue. The common method of synthesizing APC typically results in a crude product containing reaction catalyst and discoloration. Currently a multi-step precipitation process is required to produce colorless, metal- and catalyst-free APCs. This process, however, is not suitable for large scale use due to expense and labor requirements.
Removing homogenous metal catalysts from polymer solutions has been performed successfully in the past. For instance, in 2002 Sakabe and co-workers detailed a method whereby a nickel 2-ethylhexanoate catalyst was removed from a norbornene and 5-hexyl-2-norbornene co-polymerization by extracting the crude non-polar reaction mixture with a solution of lactic acid in 2-propanol and water (Patent# JP 2002284820). In another approach, Gridnev successfully decolorizes a cobalt(III) borontrifluoride catalyzed synthesis of methacrylate homo- and co-polymers by acidification, catalyst complexation using the bidentate 1-(3-aminopropyl)imidazole, and filtration through a silica gel column (U.S. Pat. No. 5,750,772). However, methods specifically suited for the removal of homogenous cobalt catalysts from aliphatic polycarbonate solutions are not currently available.